Portable jig boring fixture



April 28, 1953 D v s PORTABLE JIG BORING FIXTURE 2 SHEETS-SHEET 1 Filed Nov. 7, 1949 INVENTOR.

Jarrel/ 5. Davis April 28, 1953 J. B. DAVIS PORTABLE JIG BORING FIXTURE 2 SHEETS-SHEET 2 Filed Nov. 7, 1949 MM M H v W M a nwfl M HMHHHHiwuiw i5 2 i a I 2E2:2:5E============E=====E: 2

"In" llll m M Z Z a rlll yll f vll/ll x w 27 $2 9w i 6 5 5 W INVENTOR. gr/e 5; 02 W5 Patented Apr. 28, 1953 PORTABLE JIG BORING FIXTURE Jarrell B. Davis, Fort Worth, Tex., assignor to Consolidated Vultee Aircraft Corporation, San Diego, Calif., a corporation of Delaware Application November 7, 1949, Serial No. 125,895

2 Claims. 1

The present invention relates in general to machine tools for precision boring, and is more particularly directed to a portable fixture adapted to be secured to a work-piece and to support, guide, and automatically feed a power-driven boring bar having a cutter disposed within a pre-drilled hole in the work-piece for obtaining a precise and accurately aligned bored hole there- Heretofore it has been necessary to accurately locate and rigidly fasten or set up a workpiece and its jig on the surface table of large and relatively heavy boring equipment such as a jig boring machine, in order to obtain accurate holes within the tolerances and limits generally required in machined members forming parts of working assemblies. The work and time required to perform these operations is particularly considerable in cases where it is desired to provide bored holes in existing assemblies, since it requires the disassembly of the work and its movement to the boring machine in order to perform the operation, as well as its reassembly when the operation has been completed. It is well appreciated in the art, that the normal set up time of such jig boring equipment is in itself an appreciable factor which not only prolongs the time necessary to complete the operation, but also ties up the machine for other uses. Furthermore, there are many applications for boring operations in which the work-piece itself is entirely too large to conveniently or practically set up on an available stationary machine. In handling large and cumbersome assemblies in jig boring equipment of the latter type, there is considerable risk of damaging either the work or the stationary machine because of the difiiculty of positioning and securing one to the other during the boring operation.

The present jig boring fixture or tool as comprehended by this invention is sufficiently light and portable to permit its support upon the workpiece itself and at the same time to provide equal precision as that obtained in stationary boring machines, thus eliminating the wasteful expenditure of work required for disassembly, set up, and reassembly; and simultaneously reducing the possibility of damage to the work-piece or boring mill, especially in those instances where the work is large in relation to a stationary machine.

' It is to be noted that conventional boring equipment is relatively expensive, and because the boring of large holes in machine operations is somewhat specialized, there are many machine shops and factories which cannot afford such 5 equipment because of the infrequency of such work. Nevertheless, when an operation of this kind is required it becomes necessary to job out the work for this particular operation thus entailing additional cost and risk. The subject invention provides a simple and efficient precision boring fixture of sufiiciently low cost to permit its use by even the most modest machine shop or manufacturing operation. At the same time it provides the same, if not greater, flexibility than stationary equipment of considerably higher first cost.

The primary object of the invention is therefore to provide a jig boring fixture or tool that is sufficiently lightweight and compact to permit portability of the tool to the assembly or work-piece for the purpose of performing a boring or reboring operation.

A further object of this invention is to provide a portable jig boring fixture that is capable of being easily aligned and secured or set up within close dimensional tolerances and in such a manner that precision bored cutting to very close limits is obtained comparable with results from standard stationary boring machines.

A still further object and advantage of this invention is to provide a light, compact, and portable jig boring fixture that is capable of being secured and aligned with a work-piece and of being universally driven from conventional electric Or pneumatic power sources.

Still another object of the invention is to provide a device of the class under consideration that is simple in construction and therefore less expensive in first cost and cost of operation than presently available conventional stationary boring machines.

A still further object of the invention is to provide a portable type jig boring fixture capable of selectively supporting, guiding, and feeding a variety of boring tools from a work-piece in situ for the purpose of precisely locating, aligning, and boring holes within tolerances of plus or minus .00025".

These and other objects and advantages of the present invention will become apparent from the following detailed description and the drawings which form a part hereof, in which like numerals of references denote similar partsthroughout the several views.

In the drawing:

Fig. 1 is a front view of the portable jig boring fixture of the invention shown mounted for operation on a typical work piece;

Fig. 2 is a vertical section of the jig boring fixture;

Fig. 3 is a perspective in which a meansfor drawings constitutes a preferred embodiment thereof, and is shown in Fig. l as being secured to a typical work-piece A together with a gig};

for the purpose of accurately transferring a hole in the latter into the work-piece A. The workpiece A is represented as a rectangular-sectioned circular ring in which it is desired to accurately and precisely form a bored radial hole H. I The general form or size of the work-piece A bears no specific relation to the invention and is described and shown in the present instance merely to emphasize the flexibility and adaptability of the jig boring fixture contemplated in the present invention. The difficulty of performing a boring operation to provide the radial hole H in the work-piece A by means of conventional stationary machinery will be apparent, if it is assumed that the diameter of the work piece A is such that it would be impossible to accommodate the boring head of such equipment within the ring-like work-piece A, and difficult or impractical to support the work on the surface plate of such machinery in such a manner that the hole H could be bored from the external periphery. The general size and shape of the work-piece, however, is not a limitation to the present invention, and

it will be apparent to those skilled in the art that the tool may be utilized in a wide range of work by the provision of relatively simple clamping and hold down means designed to accommodate each particular job.

In reference to Figs. 2 and 3, the portable jig boring fixture l2 consists essentially of a base member l4, a feed plate l5, a boring bar i6, and

a universal drive cap l1.

As illustrated, the base member H3 is in the "general shape of an inverted T having an elongated square-sectioned body portion H! with integral transversely-extending projections 19 and 20, the lower faces thereof being accurately ground to provide a lower work-engaging surface 2|. The surface 2| is transversely and centrally relieved by a recess 22 of the same cross section as the body M. The body member I4 is provided with a longitudinal bore 23 accurately disposed at right angles to the plane of the surface 2| and of the recess 22, and which accommodates a journal 24 or sleeve of bronze or other suitable bearing material.

The boring bar It comprises an elongated cylindrical body portion 25 terminating at its upper end in a reduced section 26 having a transverse hole 21, and being provided at its lower end with .means for securing a variety of cutting tools, one

form of which is illustrated in Fig. 5 and which will be described hereafter. The bearing 24 of the base member l4 accommodates the body 25 of the boring bar It and is of sufiicient length and diameter to rigidly support the boring bar 16 therein for both rotation and longitudinal sliding.

The universal drive cap I? comprises an upper member 28, a universal block 29, and a lower member 30. The members 28 and 30 are each provided with a pair of axially extending ears 3| and 32 respectively between which the univer- "sal block 29 is disposed in assembly, the members e nr rm n t 'qpsm qnyt 28 and 30 being pivotally supported thereon by pins 33 and 34 disposed at to each other. A universal driving connection is thus formed between the upper member 28 and the lower member 30 so that rotation of one causes rotation of the other over a considerable angular range between their axes. The lower member 30is axially counter-bored to accommodate the reduced section 26 of boring bar It and is provided with transverse holes mating with the hole 21 of the boring bar 16 through which a pin 35 is adapted to pass to form a driving connection between the universal drive cap I! and the boring bar 16.

Y The upper member 28 of the drive cap I1 is formed with a projecting drive stub 36 of suitable diameter to be secured in the chuck or collet of an electric or pneumatic type hand motor 31.

By means of the universal drive cap l1, rotation of the boring bar l6 in the body member 6 may be accomplished through a wide range of angularity by means of the hand-type'motor 31, and in the example illustrated in Fig. .1,-'it will be seen that this result may be obtained' even though the motor 3i cannot be accommodated within the confines of the work-piece A in such a manner that a direct drive to the bar it may be obtained. In this instance, although the' center line of the boring bar is must be disposed within the periphery of the work-piece A, its rotation may be accomplished through the universal drive cap ll even though the driving motor 31 is disposed to one side or another of the work. The flexibility provided by the universal feature of the drive widens the application of the tool comprehended by the invention and permits'its use in a variety of locations where the surrounding structure confines the work area and precludes the use of more cumbersome equipment.-

The transversely extending projections l9 and 2d of the base member is are provided with centrally disposed holes 38 adjacent their extremities serving as a means for clamping the boring fixture 12 to the work. In the example shown in Fig. 1, this is accomplished by means of "a backup plate 39 adapted to be positioned against the external periphery of the work-piece Aand to be fastened securely t the base'member- M by means of a pair of bolts 40 passing through the holes 38 andinto threaded aligned holes fil in the plate 39. With the work-piece'A and jig B supported in the recess 22 or the tool l2 and with the latter disposed centrally of the hole l'fl, tensioning of the bolts 40 between the projectidns li and 28 and the back-up plate 39 rigidlysecures and aligns the tool 12 in relationto the work-piece A. The use of the back-up plate 39 in the manner shown is a particularly convenient manner of securing the tool {2 in relation to the work-piece A where the dimensions of 'the work permit access to the underside as a means 'of support. Many other forms of simple clamping and hold down means may be utilized inconnection with the portable jig boring fixture of the present invention depending upon'the'nature and configuration of the work. Additional "prelocated hole H in the jig B serves as'a guide or transfer hole for the desiredh ole' in the workhole 1 l l is 'pre-drilled through the' work p'i'ce- Ato a 5 diameter less than that of the desired finished hole, The jig B is then assembled with the workpiece A so that the hole I is aligned with the drilled hole II.

The present invention is adapted to a wide variety of cutting operations and tothis end, the lower end 42 of the boring bar It may be formed in any of a number of arrangements to accommodate cutting tools of various types and sizes. For the purpose of illustration and in connection with the present example, a rectangular-sectioned cutting tool 43 is herein shown, having a sharpened outer cutting edge 44, and being adapted to be secured transversely of the boring bar I6 adjacent its lower end 42 in such a manner that the cutting edge 44 describes a circle of the exact diameter of the desired hole when the boring bar I6 is rotated. The cutting tool 43 is adapted to fit within a transverse slot 45 in the lower end 42 of the boring bar, to be adjusted so that the cutting edge 44 projects the desired amount from the center of the bar It, and to be secured in position by a screw 46 engaging a suitable threaded hole 4? centrally located in the bottom face of the bar It and extending into the slot 45 so that the screw 46 bears against the cutting tool 43 and clamps it in the desired position.

With the jig B positioned together with the work-piece A so that the holes I9 and II are in alignment, the boring fixture i2 is then located over the hole I9 in such a manner that rotation of the boring bar It is exactly centered therein, and the assembly is then clamped by the bolts 40 and back-up plate 39 to rigidly secure the work-piece A, the jig B, and the boring tool It together in accurately aligned and adjusted relation. Rotation of the boring bar H; by means of the motor 31 and simultaneous axial feed thereof will cause the cutter 43 to bore out the pre-drilled hole II to the exact and identical dimension and position of the hole It in the jig B.

The portable jig boring fixture I2 of the invention includes means for uniformly feeding the boring bar It and its cutting tool 43 toward the work comprising the feed plate I5, a threaded feed spindle 48 and an indexing collar 49. The feed plate I is generally a flat member having a central bore 59 and two diametrically opposed holes 5| and 52. The feed spindle 48 is supported by the feed plate and secured for rotation in the hole 5| and a fixed guide shaft 53 is positioned in the hole 52 on the other side of the boring bar IE to prevent rotation of the feed plate I5 with respect to the boring bar I6 and to provide additional axial sup-port of the latter with respect to the body member I4.

A center collar 54 is adapted to encircle the body of the boring bar I6 and to be adjustably and selectively secured thereto by means of a set screw 55. A bronze sleeve 56 surrounds the collar 54 and abuts against an undercut 5! therein having an external diameter accommodating the hole 56 and forming a bearing therewith. The lower end 58 of the center bushing 54 is externally threaded to accommodate a nut 59 and a lock nut 64. The nut 59 bears against the lower face of the sleeve 56 to secure it against rotation on the center collar 54. The lock nut (it is adapted to be tightened against the nut 59 to prevent loosening thereof. With the nut 59 clamping the sleeve 56 to the central collar 54, it will be seen that when the latter is secured to the body 25 of the boring bar I6 by the set screw 55, the boring bar I6 may revolve within the feed plate l5 but that the latter will be maintained in its axial or longitudinal position with reference to the boring bar l6.

A depending sleeve 6! is pressed into the hole 5| in the feed plate l5 serving as a journal for a central cylindrical portion 62 of the feed spindle 48. The upper end of the feed spindle 48 is externally threaded at 93 to engage a central threaded bore on a knurled drive cap 64. The drive cap 64 is locked to the upper end of the feed spindle 48 by means of a washer 65 and a locking screw 56 which engages a central threaded hole 6! in the upper end of the feed spindle 48. The outer diameter of the drive cap 64 is such that clearance is provided from the outer surface of the boring bar I6 when the latter is mounted in the jig boring tool I2.

An indexing collar 49 is provided with a central bore for sliding engagement on the body 25 of the boring bar It and is adapted to be adjust ably secured thereto by means of a set screw 38. The lower surface of the indexing collar 49 is provided With an integral depending lug 69. The upper surface of the drive cap 44 is provided with a number of equally spaced upwardly extending pins III which are disposed in the path of the lug 69 as it revolves with the boring tool I5, in such a manner that the drive cap 84 is rotated or indexed upon each revolution of the indexing collar 49 an amount equal to the angular distance between the pins 18.

The lower end of the feed spindle 48 is provided with a fine pitch left-hand external thread and engages a similarly threaded bracket II supported on a lateral face I2 of the base E4. The bracket if is adapted to be secured to the face 12 by screws I3 passing through fianges I4 into mating tapped holes in the base I4. The bracket II is preferably formed of Phosphor bronze or other suitable bearing material, and may be formed with a longitudinal split between a pair of radially extending flanges I5. Cap screws I6 extending through the flanges "I5 provide a means of releasing the threaded lower portion of the feed spindle 49 from engagement with the threaded bore of the bracket I I.

The arrangement thus described exemplifies means for automatically and uniformly feeding the boring bar it towards the base member I4 as it is rotated, as it will be seen that rotation of the drive cap E4 will move the feed plate I5 toward or away from the base member I4 an amount equal to the pitch of the lower threaded end of the feed spindle 48 for each revolution of the latter, and that if the feed plate I5 is secured to the boring bar I5 by means of the center collar 54 the boring bar IE will be axially moved relative to the base member 14 in the same manner. Also, when the indexing collar 49 is secured to the body 25 of the boring bar I6 by the set screw 68, so that the lug 69 successively engage the pins Id of the drive cap 64, rotation of the boring tool It will index the feed spindle 48 and feed the boring bar It with its cutting tool 43 toward the-work.

In order to balance the rotative forces around the boring bar It and to provide additional axial support, with respect to the base member I4, a guide shaft 53 disposed on the opposite side of the boring bar I6 from the feed spindle 48 is f secured by its lower end to a bracket 11 mounted on a lateral face I8 of the base l4 aligned with and projecting upwardly through a bearing sleeve I9 secured in the hole 52 of the feed collar l5.

permitting the feed-plate- 15 to move freelytowar d and away'fromthe uppcrend of the baselmemher it, while resisting its rotation and-servingin cooperation with the feed spindle 48 as abalanced outboard support for the boring bar Hi to maintain'the latter in precise alignment with the base member Hand to oppose theradial loads impartedto the'tool l2 while the cutting tool 13 is iricontact with the work.

By loosening the set screw 55 of the collar'ibd, and the setscrew til-of the indexing collar 49, the boring bar it is released from connection'with the feed plate 15 when it is desirable to freely position the boring bar 56 in longitudinal relation with the bodymember id, as when setting thecutting-tool' li-l preparatory to initiating a boring operation. 'The feed plate this then "quickly adjustedto provide sunicient clearance betweenit and-the upper face of the body me'm ber i l by loosening-the cap screws 76' to release the threaded bracket Hfrom engagement with the lower end ofthe feed spindle 'With sunlcient'olear'ance between the bottom surface of the fedcollar"lb-andthebody member id to enable *the'cutting-tooltil' to pass through the work; the screws F8 are then tightened so that further "movementof' the two elements towards eachother can only becbt'ainedby rotation of the feed spindle 48.

An-alternate-means' o'f 'quickly setting the clearance between the feed plate 15 and the body member H3 is indicated in Fig. 3 wherein a revers- "ibleelectricchair-operated hand motor'fit =is "providedwvith'a-suitable bite! to engage the socket in the header" the screw as. By this means,

the feed spindle may be rapidly run up or down until theclesired clearance is obtained between the body'portion i4 and-the feed plate IS. The

"plate 15 may then be secured to the boring tool It by means of the set-screw 55 with the cutter A3 in its desired axial position with respect to'the "woikfandthe indexing collar 39 secured to the boring tool '16- by *theset screw (58 in such position that rotation "of the tool it causes its auto-.

"matic feeding "by"r'eason' of the engagement" of the lug 65-3 with the pins it.

As thus described, the"invention' comp-rehends a p'ortablejig' boring fixture or tool character- "ized by li glit vveight, simplicity and flexibility,

"and being capable of equal accuracy on boring Work'in situ as obtainable with conventionalgstationary equipment.

While the invention has been deseribed'in' connection wit'lrcertain specific structural details,"-

it'will be obvious to those skilled in the artthat many modifications of these details may beemployed without departing from the spirit and scope of theinvention as defined in the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A portable'prec'ision boring fixture including an inverted generally T-shaped base member Y comprising an elongated body portion having a longitudinal bore therethrough and laterally projecting work engaging portions, means for secur- "mg and positioning said base member to a workpiece, an elongated cylindrical boring bar slidably and 'rotatively movable within said bore'of the a body portion and projecting beyond opposite ends "'of the'body portion, means at one extremity of said boringibar for supporting-a work-engaging tool, feed means for progressively adjusting the longitudinalposition of said boring bar with respect to said base member during rotation of said boring bar, said feed'means comprising a T plate, means rotatively supported on said plate for selectively securing said plate to said boring bar with respect to the longitudinal axis thereof, a threaded spindle rotatively supported by said feed plate and a guide sleeve carried by said feed plate, threaded means supported by said 5 base member at one side of said boring bar having an operative connection with said threaded spindle, a guide shaft carried by said base member at the other side of said boring bar for slidable engagement with said guide sleeve, indexing means adjustably secured to said boring bar and rotatable therewith and means on said indexing means for moving said threaded spindle longitudinally with respect to said base member during rotation of said boring bar.

2. A portable precision boring fixture including an inverted generally T-shaped base member comprising an elongated body portion having a longitudinal bore'therethrough and laterally projecting work engaging portions, means for securing and positioning said base member to aworkpiece, an elongated cylindrical boring bar slidably and rotatively journaled within said bore of the body portion and projecting beyond opposite ends of the body portion, means at one extremity of said boring bar for supporting a work-engaging tool, feed means for progressively adjusting the longitudinal position of said boring bar with respect to said base member, said feed means comprising a plate, collar means rotatively supported on said plate for-selectively securing said plate to said boring bar with respect to the longitudinal axis thereof, a threaded spindle rotatively supported by said feed plate, a plurality of equally spaced projecting members supported at an end of said threaded spindle and a guide sleeve carried by said feed plate, threaded means supported by said base member at one side of said boring bar having an operative connection with said threaded spindle, a guide shaft rigidly secured to said base member at the other side of said "boring bar for slidable' engagement with said guide sleeve, and indexing means comprising a collar adjustably secured to said boring bar and rotatable therewith, said collar having a depending portion engageable with said projecting members carriedby said threaded spindle for moving said threaded spindle longitudinally with respect to said base member during rotation of said boring bar.

-JARRELL B. DAVIS.

II References Gitcd in the file of this patent 

